Method of sizing synthetic linear polymer yarns



Patented Aug. 19,1941

METHOD OF SIZING SYNTHETIC LINEAR POLYMER YARNS Edgar W. Spanagel, Wilmington, Del., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application October 29, 1938, I

Serial No. 237,789

18 Claims.

This invention relates to a new and improved sizing composition for such textile filaments and yarns as are quite insensitive to water and to which the usual sizing compositions adhere with difliculty.

Carothers in U. S. Patents Nos. 2,071,250, 2,071,251 and 2,071,253 describes an entirely new class of compounds, namely, synthetic linear polymers, and filaments comprising them.- The filaments can be formed by spinning directly from the molten material without the use of solvents such as are used in the preparation of other synthetic filaments. A notable property of these filaments is their capability of being cold drawn (stretched in the solid state) whereupon they become oriented and exhibit great strength and true elasticity (both bending and tensile elasticity). This melt spinning process results in filaments of great smoothness andslickness. By the term smoothness is meant the absence of crenulations and theflike from the surface of the filaments and by "slickness is meant the low coefiicient of friction of the surface of the filaments or of the yarn comprising them.

These filaments are insoluble'in substantially all common solvents and are little affected by contact with water; the ratio of their wet strength The manufacture of fine stockings is, at best, a delicate operation and the cost of the finished product is a reflection vof the convenience of opdown after leaving the needles and sinkers resultto their dry strength being much higher than for other textile filaments. Another very interesting and useful property of these filaments is their ability to become set in the condition or shape in which they are first exposed to. steam, hot water, hot alcohols and other non-solvent swelling agents. After a setting treatment the filaments when deformed tend to return, after the deforming forces are removed, tothe shape inwhich they were set.

Of these synthetic linear polymers, the polyamides are particularly interesting. The synthetic linear polyamides are of two types, those obtainable from mono-aminomonocarboxylic acids and those obtainable from the reaction of suitable diamines and dibasic carboxylic acids. The diamine-dibasic acid derivatives are more fully described in the U. S. Patent No. 2,130,948. For convenience, this invention shall be discussed in'terms of these polyamides, particularly of polyhexamethylene adipamide which is obtainable from the reaction of hexamethylene diamine and adipic acid, although the invention is not so limited.

The remarkable properties of these synthetic linear polyamide filaments and more particularly the yarns comprising them have made it possible to use them for a variety of purposes. Notable among these uses is the production of hosiery, particularly Prior to the development of these synthetic polyamide yarns, high grade stockings have been made almost exclusively from natural silk.

full-fashioned -hosiery.

ing in a closely knitted fabric with narrow wales, causing difficulty in the topping operation and resulting in the formation of frequent runs. nally, .the elasticity of the yarn tends to cause the loops in the knitted fabric to shift until set with the production of imperfect stockings ,by reason of these bad stitches.

It was found that the usual sizing compositions commonly employed for textile yarns failed to relieve these conditions, one important reason being that the conventional sizing compositions did not adhere to these polyamide yarns. The successful development of a stocking industry based on these polyamide yarns was, therefore, contingent on a satisfactory size composition.

The object of this invention is to provide a sizing composition for polyamide yarns which will promote good snag resistance, which will definitely reduce edge rolling of the flat knit fabric and which will make for good final'stitch formation.

The object of the invention is accomplished by the use of a'sizing composition comprising polyalphamethacrylic acid. I

Although the preparation of the polyalphamethacrylic acid, hereinafter referred to as polymethacrylic acid, is not within the scope of this invention, a suitable polymer may be conveniently prepared by direct polymerization of the purified monomeric material in water. The monomeric material has the formula This solution of the polymer may be used directly without isolation of the polymethacrylic acid or it may also be used in solution in organic solvents.

The natureof the invention will become more acrylic acid (having a viscosity of 4.5 poises in methyl alcohol solution) in ethyl alcohol on a Wildman full-fashioned knitting machine.-

The yarn was moistened just before it reached the needles and sinkers of the knitting machine by passing it over a wick wet with water. This moistenlng rendered the sizing composition plas- The v tic and facilitated good loop formation. humidity and temperature of the knitting room was so adjusted that the knit fabric dried sufficiently to destroy the plasticity of the sizing composition before :the fabric was removed from the knitting machine thus holding the desired loop formation in the fabric until it could be set;- Similarhi sized polyhexamethylene adipamide yarns of the proper denier and twist were used in the toe, welt, heel and sole. This fabric had little edge roll, good snag resistance, well formed stitches, and open loops. Following knitting, the

"stocking was looped and seamed in the customary manner, placed on a boarding form and' treated with saturated steam to set the yarn in the ,desired conformation. The stocking was then removed from the form and subjected to scouring, dyeing, rinsing, finishing and reboarding operations. The completed stocking had an attractive appearance, excellent stitch formation and good fabric elasticity.

Example 11 A skein of denier, 20-turn polyhexamethylene adipamide yarn was treated as in Example I in an aqueous bath containing 8% polymethacrylic acid, 10% triacetin and 0.2% of Gardinol WA (the sodium salt of sulfuric acid ester I of lauryl alcohol). The yarn was used in knitting stocking fabric on a Wildman full-fashioned knitting machine. The yarn was moistened just before knitting and'the knitted fabric was dried immediately after it left the needles and sinkers by a current of warm air. The yarn knit well, producing a fabric of excellent stitch formation which showed practically no edge rolling and which had no pulled threads.

Example III An aqueous solution was prepared containing 6% of polymethacrylic acid, 4% of glycerol, and 0.5% of Textile Softener No. 3 (a' commercial water-emulsifiable mineral oil). This solution was applied to a polyhexamethylene adipamide' yarn on a spool to spool sizing machine in which the yarn was taken fromv a twister pirn A sewing thread was prepared by plying together three l-denier, '75-filament, 12-turn S" twist oriented polyhexamethyleneadipamide yarns with 8 turns Z twist. 'The sewing thread was then treated as inExample I in an aqueous bath containing 10 g./liter of'polymethacrylic acid and 10 g./liter of glycerin and 0.6% of a mixture of 50% oleyl diethyl ethylene di'amine ethyl sulfate. and 50% dextrin, and dried at room temperature. The resulting sewing thread performed very well at high speeds, did not undergo appreciable abrasion on commercial sewing machines and gave seams of good strength. Sewing threads so prepared are valuable for use in the looping and seaming of these synthetic polyamide stockings.

The above examples illustrate the use of sizing compositions for these polyamide yarns comprising polymethacrylic acid. There is a' unique cooperation between the polyamide yarn and the polymethacrylic acid. Importantly, polymethacrylic acid adheres to the yarn, which adhesion is a strict requirement for a size. That polymethacrylic acid adheres to the yarn is surprising, considering the fact that the acid can be applied from a water solution, and that the filaments are notably insensitive to water and other common solvents, not to speak of the fact that the filaments are slick and smooth, which in itself complicates the sizing problem. Not only is it true, as indicated previously, that the prior art sizing compositions do not adhere satisfactorily to these polyamide yarns, but it is also true that of the many vinyl and acrylic compounds known, only the use of the following has been found at all successful: of primary importance polymethacrylic acid and, to less preferred extent, interpolymers of methacrylic acid with acrylic acid, and to some extent polyacrylic acid; also interpolymers of methacrylic acid with styrene, vinyl acetate and/or methyl methacrylate, providing the interpolymers contain less than 10% of the latter materials. The salts andesters of polymethacrylic acid and polyacrylic acidas well as salts and esters of their interpolymers are not satisfactory for this purpose.

The size compositions of this invention are capable of being easily and rapidly dried at a reasonably low temperature so that there is little danger of prematurely setting 'the polyamide yarn, which setting would tend to seriously interfere with good final stitch formation. The size is also capable of being easily softened by moisture .so'that a temporary condition of plasticity can be developed at the moment of knitting, after which it can be readily dried, reducing the plasticity' and holding the stitches in the desired conformation until they can be set. The rapid rate at which yarns sized with these tions may be dried effects an important in the sizing operation. This is especially true in continuous sizing operations permitting size applications at a very rapid rate.

, Most important, the size is capable of sofincomposiishing the yarn and of so holding the filaments together as a unitary structure as to resist snagging during the operation of knitting, looping, seaming, topping, etc., to the end that a stocking is produced which is free from pulled threads and, therefore, a high stockings is assured. 1 It is also found that the flat knit stocking sized with the composition has a greatly reduced tendency to roll on itself with the result that the 1 looping and seaming operation can be performed very simply and quickly and without the pro- ,fductionof snags which would certainly resultif a considerable amount of manipulation was reeconomy percentage of satisfactory the balloon of the downtwister.

quired to get the fabric in condition for looping and seaming.

The knitting of stockings and other goods with polyamide yarns presents a difficulty of main-.

which makes them so interesting for use in stock ings tends to militate against the. convenient knitting of them into a series of needle and sinker loops and the elasticity of the yarn must in some way be controlled during the course of the process. It should also be observed that the size can be very easily removed by treatment in aqueous solutions when it has served its purpose. This in itself is surprising for the reason that because of the known water-insensitivity of these yarns, it might be expected that a sizing composition which adheres does so as the result of some sort of a chemical interaction and that its removal would involve difllculty.

While the invention has beendescribed with reference to the application ofthe ,polymethacrylicacid from water and alcohol solutions, it is obvious that it can be applied from solutions in other solvents. been described with reference to the application of the compos tion by the immersion of skeins in the size bath and continuously by passing the yarn through the baths. It is apparent that this operation can be carried out in a variety of other ways; for example, the application might be combined with the cold drawing operation. After drawing, the yarn can be passed through a bath on the windup bobbin. Since it is often convenient to combine the cold drawing operation and twisting on a downtwister, it may be convenient to apply the composition between the draw rolls and the downtwister. This procedure has the advantage that the treated yarn may be dried in Similarly, drying may be facilitated by the use of volatile solvents for the polymethacrylic acid.

It, is within the spirit of the invention and as indicated in the above examples, it is often desirable to modify the sizing composition by the addition of various materials. Thus the softness and smoothness of the treated yam may be modified by the addition of material, such as glycerol, glycols, esters of glycerol, such as triacetin and glyceroltriglycollate, sulfonated oils, dextrin, urea, ethanol formamide, etc. Among other things, these materials tend to make it easier to temporarily soften the sized yarn when the yarn is moistened with water at the instant of knitting, To further expedite this temporary treatment, wetting agents, such as Gardinol" WA, may be added to the composition if desired. Theinvention also contemplates the addition of lubricants to the composition where the presence of a lubricant on the flnalyarn is found desirable. Itis true that the sizing of the yarn permits the filaments to operate as a unitary structure, prevents the formation of pulled threads bysetting up a snag resistance, insures Similarly, the invention has poration of a textile lubricant in the compositions. Materials which are suitable for this purpose are mineral, vegetable, and sulfonated oils, soaps, such as triethanolamine oleate, and a variety of other materials such as diglycol oleate, glycerol monoricinoleate, etc.

The lubricants added to the sizing composition can also be added before or after and independent of the size composition. For example, it might be desirable to incorporate the lubricant into the water which usually moistens the yarn just beor over a. roller immersed in the bath and dried l of the fact that the sizing composition prevents freedom from edge rolling of the flat knit fabric,

and,,in general, promotes the manufacture of flnestockings. It will frequently be found, however, that further improvement in the general running qualities may be achieved by the incorfore knitting. This can easily be accomplished when the textile lubricant chosen is one which is water-soluble or water-emulsifiable.

Various coning oils may .be applied to the yarns sized according to the invention. Examples of such compositions include olive, tea seed and and at the same time act as a lubricant and/or wetting agent.

Similarly, some of the modifiers mentioned may act as buffers to maintain at any desired value the pH of the size bath or of the size on the yarn when moistened prior to knitting. That the size composition is not strongly acid is generally desirable to prevent undue corrosion of the needles and sinkers on the knitting machine. Other corrosion inhibitors may be added. Examples of other materials which may be added to the wetting trough of the knitting machine for various purposes include commercial triethanoi amine and its fatty acid esters, diglycol oleate, morpholene, pyridine, etc.

It will be seen, therefore, that the invention contemplates the use of a sizing composition for these polyamide yarns which comprises polymethacrylic acid and certain interpolymers of methacrylic acid, or in less preferred sizing compositions, polyacrylic acid. .It will be seen that the invention contempiates a polyamide yarn well sized and well capable of being used in textile operations as may be desired and where a size performs a useful function. It will. be found that the size adheres well to the yarn and resists mechanical removal which might result from the forces involved in a twisting operation or by rubbing against thread guides, etc. It will be found that the thread so sized even though it be made of a very large number of very finefilaments, will operate as a unitary structure and will havea high degree of snag resistance to the end that very few filaments will be broken and the final fabric will be quite free from pulled threads. In the case of full-fashioned hosiery, it will be found that the looping and seaming operation proceeds very conveniently and very successfully by reason edge rolling of the flat knit fabric and holds out the loops for ready manipulation. It will be found, too, by reason of the fact that the sizing composition can be temporarily softened, that in spite of having a yarn with a remarkable high elasticity, it is possible to form a fabric having a very orderly stitch formation. It will be found that the size can be very easily removed when it ,has served its purpose without danger of damaging the fabric, however delicateit may be.

,Two to 6% by weight of the. polymethacrylic acid, based on the weight of the yarn, results in optimum performance and this exceedingly small amount of size on polyamide yarn, together with its ease of removal, constitutes a notable saving both in the reduction of the time required for application and loss in weight involved, and also in the reduction in damage to the yarn itself and particularly to other components in a mixed fabric of the character of cellulose acetate rayon. By way of comparison, the sericin on natural silk occurs to an extent of 20-24% and is not easily removed to a point where, in a mixed fabric, a cellulose acetate rayon component is. definitely damaged during'the course of the removal of the sericin from the silk.

An important but minor advantageof this sizing composition on these polyamide yarns is that in spite of its being readily soluble in water and of adhering well to the yarn, a solution of this size is capable of being dried easily. This property makes it possible to apply the size continuously and dry it continuously, e. g., at 500- 1100 ft./min. while the maximum speeds possible with prior art size have, in general, not exceeded 50-125 ft./min. In modern industry the investment in fixed costs is so high-that speed in operation is an important element of management. These polyamide yarns should not be dried at elevated temperatures for the reason that a premature setting of the yarn would be obtained which would tend to defeat the entire procedure.

' other hand represent a highly critical situation from the point of view of snag resistanca edge rolling and perfection of stitch. It is obvious, of course, that this invention is equally applicable to monofilament yarns, staple fibers, spun yarns, mixed yarns, films, ribbons, and the like comprising synthetic polyamides, and that it is equally useful for other textile operations such as weaving, sewing and the like. Ina similar fashion, the invention has been discussed specifically in terms of polyamide yarns. It will, however, be found, in general, that this sizing composition is uniquely useful for those other synthetic yarns which also are quite insensitive to water and where difiiculty of adhesion with the usual sizing compositions is involved. The sizing composition of this invention is also valuable in the treatment of textile filaments composed of other synthetic linear polymers includingpolyesters, polyethers, polyacetals, mixed polyesterpolyamides, etc., which, for example, may be prepared by a process of condensation polymetrizationas described in U. S. Patent No. 2,071,250. These sizing compositions are also suitable for sizing of filaments and yarns composed of the polymers prepared'by high pressure polymerization of ethylene which are described in the copending application of Fawcett et al., Serial No. 123,722,'filed February 2, 1937; also for sizing yarns of ingrain sllkin view of the definite advantage of ease of removal over sericin.

Since it is obvious that many changes and modifications can be made in the details above described without departing from the nature and spirit of the invention, it is to be understood that the invention is not to be limited except as set forth in the appended claims.

I claim:

1. A textile yarn comprising filaments of a crystalline syntheticlinear polymer taken from the class consisting of polyesters, polyethers and polyamides containing a coating of a sizing composition comprising a compound taken from the group consisting of polymethacrylic acid, an interpolymer of methacrylic acid with acrylic acid, polyacrylic acid, an interpolymer of methacrylic acid with. less than 10% of styrene, an interpolymer of methacrylic acid with less than 10% of vinyl acetate and an interpolymer of methacrylic acid with less than 10% of methyl methacrylate. l

2. A textile yarn comprising filaments of a crystalline synthetic linear polymer taken from the class consisting of polyesters, polyethers and polyamidescontaining 2% to 6% by weight of a coating of a compound taken from the group of styrene, an interpolymerof methacrylic acid consisting of polymethacrylic acid, an interpolymer of methacrylic acid with acrylic acid, polyacrylic acid, an interpolymer of methacrylic acid with less than 10% of styrene, an interpolyamides containing 2% to 6% of a coating of polymethacrylic acid.

5. A textile yarn, comprising filaments of a crystalline synthetic linear polyamide containing a coating of a sizing composition comprising a compound taken from the group consisting of polymethacrylic acid, an interpolymer of methacrylic acid with acrylic acid, polyacrylic acid, an interpolymer of methacrylic acid with less than 10% of styrene, an interpolymer of methacrylic acid with less than 10% of vinyl acetate and an interpolymer of methacrylic acid with less than 10% of methyl methacrylate.

6. A textile yarn comprising filaments of a crystalline synthetic linear polyamide containing 2% to 6% by weight of a coating of a compound taken from the group consisting of polymethacrylic acid, an interpolymer of methacrylic acid with acrylic acid, polyacrylic acid, an interpolymer of methacrylic acid with less than 10% with less than 10% of vinyl acetate and an interpolymer of methacrylic acid with less than 10% of methyl methacrylate.

'7. A textile yarn comprising filaments of a crystalline synthetic linear polyamide containing a coating of asizing composition comprising polymethacrylic acid. g

8. A textile yarn comprising filaments of a crystalline synthetic linear polyamide containing 2% to 6% of a coating of polymethacrylic acid.

9. A textile yarn comprising polyhexamethyl-.

ene adipamide filaments containing a coating. of a sizing composition comprising a compound taken from the group consisting of polymethacrylic acid, an interpolymer of methacrylic acid with acrylic acid, polyacrylic acid, an interpolymer of methacrylic acid with less than of styrene, an interpolymer of methacrylic acid with les than 10% of vinyl acetate and an interpolymer of methacrylic acid with less than 10% of methyl methacrylate.

o 10. The process of rendering textile yarns comprising filaments of a crystalline synthetic linear polymer taken from the class consisting of polyesters, polyethers and polyamides resistant to snagging and capable of being knit into fabrics which will retain a uniform loop formation which comprises applying to said yarns a compound taken from the group consisting of polymethacrylic acid, an interpolymer of methacrylic acid with acrylic acid, polyacrylic acid, an interpolymer of methacrylic acid with less than 10% of styrene, an interpolymer of methacrylic acid with less than 10% of vinyl acetate and an interpolymer of methacrylic acid with less than 10% of methyl methacrylate.

11. The process of rendering textile yarns comprising filaments of a crystalline synthetic linear polymer taken from the, class consisting of polyesters, polyethers and polyamides resistant to snagging and capable of being knit into fabrics which will retain a uniform loop formation which comprises applying to said yarns 2% to 6% by weight of a compound taken from the group consisting of polymethacrylic acid, an interpolymer of methacrylic acid with acrylic acid, polyacrylic acid, an interpolymer of methacrylic acid with less than 10% of styrene, an interpolymer of methacrylic acid with less than 10% of vinyl acetate and an interpolymer of methacrylic acid with less than 10% of methyl methacrylate.

12; The process of rendering textile yarns comprising fllaments of a crystalline synthetic linear polymer taken from the class consisting of polyesters, polyethers and polyamides resistant. to snagging and capable of being knit into fabrics which will retain a uniform loop formation which comprises applying to said yarns polymethacrylic acid.

14. The process of rendering textile yarns comprising filaments of a crystalline synthetic linear polyamide resistant to snagging and capable of being knit into fabrics'which will retain a uniform loop formation which comprises applying to said yarns a compound taken from the group consisting of polymethacrylic acid, an interpolymer of methacrylic acid with acrylic acid, polyacrylic acid, an interpolymer of methacrylic acid with less than 10% of styrene, an interpolymer of methacrylic acid with less than 10% of vinyl acetate and an interpolymer of methacrylic acid with less than 10% of methyl methacrylate.

15. The process of rendering textile yarns comprising filaments of a crystalline synthetic linear polyamide resistant to snagging and capable of being knit into fabrics which will retain a uniform loop formation which comprises applying to said yarns 2% to 6% by weight of a compound taken from the group consisting of polymethacrylic acid, an interpolymer of methacrylic acid with acrylic acid, polyacrylic acid, an interpolymer of methacrylic acid with less than 10% of styrene, an interpolymer of methacry1ic acid with less than 10% of vinyl acetate and an interpolymer of methacrylic acid with less than 10% of methyl methacrylate.

16. The process of rendering textile yarns comprising filaments of a crystalline synthetic linearpolyamide resistant to snagging and. capable of being knit into fabrics which will retain a uniform loop formation which comprises applying to said yarns polymethacrylic acid.

17. The process of rendering textile yarns comprising filaments of acrystalline synthetic linear polyamide resistant to snag ing and capable of being knit into fabrics which will retain a uniform loop formation which comprises applying 13. The process of rendering textile yarns com-.

prising filaments of a crystalline synthetic linear polymer taken from the class consisting of polyesters, polyethers and polyamides resistant toto said yarns 2% to 6% polymethacrylic acid.

' 18. The process of rendering textile yarns comprising polyhexamethylene adipamide filaments resistant to snagging and capable of being knit into fabrics which will retain a uniform loop formation which comprises applying to said yarns a compound taken from the group consisting of polymethacrylic acid, an interpolymer of methacrylic acid with acrylic acid, polyacrylic acid, an interpolymer of methacrylic acid with less than 10% of styrene, an interpolymer of methacrylic acid with less than 10% of vinyl acetate and an interpolymer of methacrylic acid with less than 10% of methyl methacrylate.

EDGAR W. SPANAGEL. 

